On a typical mass transit vehicle there are a number of electromechanical switches for operation by the crew of the vehicle in order to control the operation of the doors. Such electromechanical switch actuators are key switch actuated. In other words, when a key is inserted into the switch actuator, the crew of the vehicle may operate an electromechanical switch that is used to control the operation of the doors. Without access to the key, the switches that control the doors are inoperable. Thus, an unauthorized person, who does not have a key, cannot open or close the doors and create an unsafe condition for the riding public.
One type of electromechanical switch that may be present on such a vehicle is known as a "crew switch." A crew switch is a switch that controls the opening and closing of a single door on a single vehicle in order to permit access to the vehicle by the crew and by maintenance personnel. Typically, one crew switch is found on the outside of each transit car and two other crew switches are found on the inside of each car in the passenger compartment, one to control the doors on the left side of the car and, another, to control the doors on the right side of the car.
Another type of electromechanical switch that may be present on a mass transit vehicle is a "door control switch." A door control switch is located in the cab of the transit vehicle, rather than in the passenger compartment. When a key is inserted into the door control switch actuator by the motorman in the cab and activated, the motorman is able to control the opening of the doors in the passenger compartment throughout the train during regular service.
Typically, crew switches have been cam-operated limit switches. Door control switches, on the other hand, have been rotary switches. One type of electromechanical key switch actuator for use as a door control switch and that is known in the prior art is set forth in U.S. Pat. No. 4,611,104-Reddy. The Reddy patent discloses an electromechanical key switch actuator for use in controlling a rotary switch for door control. The actuator of the Reddy patent is straddle mounted on the wall of the cab of the mass transit vehicle. In other words, the actuator is situated on the inside of the cab of the vehicle and the rotary switch to which the actuator is coupled is situated on the inside of the electrical control box on the opposite side of the cab wall. The Reddy actuator also includes a forwardly projecting boss projecting forward of an indicator face. A shaft is situated within the boss. A key is inserted into the boss and is designed to mate with the shaft. The key includes an insert end that includes a cavity therein. The cavity mates with the shaft within the boss. The configuration of the key and boss are such as to permit entry and withdrawal of the key at certain preselected angular positions but to preclude entry and withdrawal of the key at other angular positions.
It would be desireable to provide a key switch actuator for use as a crew switch that employed the same key used to operate the door control switch so that the crew of the mass transit vehicle need carry only a single key. However, certain features of the switch actuator of the Reddy patent make that actuator unsuitable for use as crew switch. First, the actuator of the Reddy patent is straddle mounted. While straddle mounting is tolerable in the cab of the transit vehicle, as in the case of a door control switch, that type of mounting is unsuitable in the passenger compartment because there is insufficient axial clearance for a straddle mounted actuator. In addition, the axial dimension of the switch actuator of the Reddy patent is such that it is unsuitable for use as a crew switch actuator. Because a crew switch, unlike the door control switch of a mass transit vehicle, is located in the passenger compartment, rather than in the cab, it is important that the actuator be flush with the vehicle wall.
Another problem associated with the actuator of the Reddy patent is the fact that the central shaft is part of a switch stop plate. The switch stop plate includes a radially projecting stop mechanism and an indicator face. The stop mechanism precludes over-rotation of the switch. The indicator face provides a visual indication of the switch position when the key is removed from the device. Because of the radial projection of the switch stop plate, however, it is necessary that the switch stop plate and the forward shaft projecting from it be manufactured by a metal casting process. Such a procedure is costly and causes the Reddy actuator to be unduly expensive.
A need has arisen for a rotary crew switch actuator that is more reliable than the cam activated crew switches of the prior art. A need has also arisen for a rotary crew switch actuator that can be flush mounted on the vehicle wall.
It is also important that any crew switch actuator be manufactured simply and at a low cost and yet include a provision to preclude over-rotation of the switch.
Finally, a need has arisen for a crew switch actuator that is not only key actuated but also that may be actuated with the same keys that are used for door control, such as the keys that are currently used to actuate door control switches in the manner of the Reddy patent.
Accordingly, it is the general object of the present invention to develop a low-cost rotary crew switch actuator.
It is a further object of the present invention to provide a rotary crew switch actuator that is key actuated with keys compatible with door control switch actuators of the type generally set forth in the Reddy patent.
It is still a further object of the present invention to provide a rotary crew switch actuator that has a small axial dimension.
It is still a further object of the present invention to provide a rotary crew switch actuator that is flush mounted, as opposed to straddle mounted, to the wall of a mass transit vehicle.
It is still a further object of the present invention to provide a crew switch actuator that may be manufactured simply and economically without the need for a metal casting process and yet which includes a means to preclude over-rotation of the switch.
These objects are met by the improved electromechanical switch actuator of the present invention.